Q. My friend Dave has three yew shrubs alongside his porch. They are over 4 feet tall and almost as wide. I have offered to help him get them under control but I want to be sure that if I prune them back hard they will come back. I understand that conifers may not get new growth when they are cut back too severely. Thanks, Ron Lewis – University Place, WA
A. Hello Ron. You are right that most conifers do not respond well to heavy pruning to control their growth. This is because there is little to no new growth that will form on older wood. Only new growth (current season) reliably will send out new growth. This is why only light pruning is recommended and thinning pruning that does not have the intent of forming new growth. The Yew (Taxus spp.) is an exception to this rule and latent buds in older growth will break when released by pruning cuts above them. The yews (and the yew family) are also exceptions in other ways from the conifers whose name implies cone bearing. The yew instead of bearing multiple seeds in a cone bears a single seed inside a pseudo-fruit. The pseudo fruit forms from the tissue where the seed attaches to the plant rather than from the any reproductive tissue (ripening ovary) as in most true fruits. This pseudo-fruit forms the distinctive cup around the seed. Now back to pruning the yew. Most likely the yew was sheared which keeps the yew rounded but doesn’t control its size very well. As you are suggesting deeper cuts are necessary since surface-heading cuts will only promote growth just behind the cuts. You should determine where the new perimeter of the shrub will be and then hand prune branches back inside this perimeter. Also look for multiple leaders that may have formed from the shearing and reduce them to a single leader especially if you would like the shrub taller than wide. Remove any branches that grow back into the center of the tree. Also make sure the top of the tree is narrower than the bottom to allow for good light penetration.